A problem with CMOS and bipolar integrated circuits (ICs) is single-event latch-up (SEL). Advanced-technology CMOS and bipolar integrated circuits intrinsically include parasitic bipolar p-n-p and n-p-n transistors that form a circuit equating to a silicon controlled rectifier (SCR) p-n-p-n. SEL occurs when a spurious current spike, introduced by cosmic neutron or other charged particle, activates the SCR creating a low impedance path and causing a large amount of current flow between the IC's power supply pins Vcc and Vss, thereby disabling the integrated circuit. A SEL is a potentially destructive condition which may or may not cause permanent damage to the circuit, but causes loss of circuit functionality.